196

WIRELESS TELEGRAPHY

former secondary to the spark gap, also by placing sufficiently large chok<3
coils in the primary side (82, Fig. 240) of the transformer.

As to the first-named difficulty, much depends upon whether a ver>r
high discharge frequency—e.g., 500 to 2000 per second for "tone trans-
mitters"—or a low frequency, say 5 to 25 per second, is used. With th.o

D

FIG. 241.

higher frequencies, the use of rotating spark gaps [see Art. 1186] is probably
not feasible, if the energy handled is large.

With the low frequencies, the various operating difficulties can "bo
very ingeniously overcome by the arrangement98 employed by the TELK-
FUNKEK Co. under the name of "resonance inductor" or "resonances
transformer."

Spark
FIG. 242.
The transformer (or induction coil) has an open core; its terminals are*
connected to the condenser circuit in the usual manner (Fig. 241). Tbu%
spark gap, E, is so adjusted in length that the normal secondary potential
is far below that necessary to jump across the gap. We then have the*
case discussed in Arts. 67 and 68: an undamped oscillating primary
circuit (armature of the alternator, coil D3 and primary coil, $1, of